Conventional microelectronic devices are manufactured for specific performance characteristics required for use in a wide range of electronic equipment. A microelectronic bare die, for example, includes an integrated circuit and a plurality of bond-pads and/or redistribution layer (RDL) pads electrically coupled to the integrated circuit. The bond-pads can be arranged in an array, and a plurality of solder balls can be attached to corresponding bond-pads to construct a “ball-grid array.” Conventional bare dies with ball-grid arrays generally have solder balls arranged, for example, in 6×9, 6×10, 6×12, 6×15, 6×16, 8×12, 8×14, or 8×16 patterns, but other patterns are also used. Many bare dies with different circuitry can have the same ball-grid array but different outer profiles.
Bare dies are generally tested in a post-production batch process to determine which dies are defective. In one conventional test process, several bare dies are placed in corresponding test sockets of a test tray. FIG. 1 is a schematic side cross-sectional view of a typical test socket 20 carrying a bare die 60 in accordance with the prior art. The test socket 20 includes a body 22 having a recess 24 and a shelf 34 in the recess 24. The shelf 34 supports an outer perimeter region of the bare die 60, and solder balls 68 on the die 60 are positioned within an opening 36 defined by the shelf 34. The test socket 20 is movable relative to a tester interface 90 so that contacts 92 on the tester interface 90 can apply electrical signals to corresponding solder balls 68 for testing the bare die 60.
One problem with conventional test sockets is that debris can accumulate within the sockets, which damages and contaminates the bare dies. More specifically, particles and contaminants from other processes, such as chemical-mechanical planarization, vapor deposition, etc., may be carried to the test socket 20 on the bare dies. This debris can accumulate in the test socket and eventually scratch, impinge, pierce, contaminate and/or otherwise damage subsequent bare dies. For example, during processing, the test socket 20 illustrated in FIG. 1 can collect debris on the shelf 34, and when a bare die is placed into the socket 20, the debris can puncture the soft, protective coating on the surface of the die and damage its internal circuitry.
Another problem with conventional test sockets is that the solder balls may not be aligned with the test contacts. More specifically, if the profile of a bare die is slightly out of tolerance, the solder balls on the die may not align with the test contacts. In the test socket 20 of FIG. 1, for example, the die 60 is aligned with the tester interface 90 by positioning ends 65 of the die 60 against side surfaces 27 of the socket 20. As such, if the profile of the die 60 is out of specification, such as if the length L of the die 60 is too short, the solder balls 68 may not be aligned with the test contacts 92 and the die 60 may fail the test even though the die 60 otherwise functions properly.
Another drawback of conventional test sockets is that the sockets limit the space available on bare dies for ball-grid arrays. For example, because the shelf 34 of the test socket 20 of FIG. 1 supports the outer perimeter region of the die 60, the outer solder balls 68a must be spaced inward at least a distance S from the corresponding ends 65 of the die 60. The reduced area for solder balls is a significant problem on bare dies with small profiles or high solder ball counts.
Accordingly, there is a need for an improved test socket for carrying bare dies and other microelectronic devices.